Why do some objects not show up in the camera view?
The Blender camera has clipping.  It has a start and end distance.  Basically it limits the rays from the camera that Blender has to render, and that can speed up render time (varies).

So right below the panel in the upper right of your screen (and the default view layout), click on the camera icon, and then under "lens", you can find the clipping start and end.



Go to your camera view (numpad 0 or view -> camera) and increase the "end" value until your entire scene is properly in the camera.  Also, make sure that the camera can currently see the most of the scene (maybe at it's furthest away point) when you do that so that it doesn't clip some things in certain positions.  I recommend increasing the "end" value past that point at least some just to make sure it is good.